Most conventional semiconductor power diodes are almost exclusively formed using silicon (Si). Due to the relative maturity of the use of this semiconductor, the performance of conventional power diodes to carry high currents and block high voltages is closely approaching the theoretical limit for Si. For example, power PiN and Schottky diodes made using Si have undergone many improvements over the past two decades allowing them to block 30 to 1200 volts while providing low on-state resistance values. However, the blocking voltage offered by Si limits the application of schottky diodes to about 250 V (because they rely on drift current transport). Therefore, high voltage devices require the use of bipolar PiN diodes. While PiN diodes provide acceptable on-state performance, they suffer from slower switching speeds.
There are many applications for power diodes that require the ability to carry high currents and block voltages in the range of 600 V to 15 kV (and greater). These applications include motor control, power supply, lighting ballast, power transmission and generation, and utility power conversion. Unfortunately, the overall performance of power diodes made using Si is poor for this voltage range, and the lack of such power diodes represents the primary limitation in realizing circuits for these applications. In fact, if high voltage diodes that support such high currents and operate at frequencies of one to 100 kHz were available, they would revolutionize power utility applications and result in substantial power savings.